1. Field of the Invention
The present invention relates to a fisheye lens system for an SLR camera and, in particular, to a fisheye lens system having an angle of view of 170 degrees or more.
2. Related Background Art
A fisheye lens having an angle of view of 170 degrees or more has been proposed, for example, in Japanese Patent Publication No. 49-20534. In a recent interchangeable lens SLR camera system, an interchangeable lens is used not only for an SLR camera having a 35 mm film format (image size: 36×24 mm, diagonal length: 43.2 mm), but also for an SLR camera having an APS film format (image size: 30.2×16.7 mm, diagonal length: 34.4 mm). Moreover, the same interchangeable lens is used for a digital SLR camera having a solid state imaging device such as a CCD (for example, image size: 23.7×15.6 mm, diagonal length: 28.4 mm).
When the same interchangeable lens is attached to the above-described three kinds of SLR cameras (35 mm film format, APS film format, digital SLR), there has been a problem that the angle of view of the images are different with each other. The problem becomes serious when a fisheye lens requiring an angle of view of 170 degrees or more is used. When a fisheye lens for a 35 mm film format SLR camera is attached to a digital SLR camera, the angle of view becomes severely narrow, so that a special effect of a fisheye lens becomes difficult to be obtained.